Why not? Because Jobs says that 7-inch diagonal screens -- which are less than half the size of the iPad's screen -- are simply not big enough. To run the type of software that differentiates a tablet from a smartphone, you need more screen real estate.

It's always possible this is Jobs talking out of both sides of his mouth -- that someday, Apple will introduce a 7-inch iPad and proclaim it the greatest device in the world. (Or maybe an 8-inch iPad, or 9-inch, etc.)

And, as frequent iPad users, we'd love something that's lighter and more portable. But we don't want to sacrifice utility for it.

Jobs really spent a lot of time bashing this idea, and it sounded like he was sincere. And Apple's testing seems to suggest that a 7-inch iPad would be inferior. So don't expect one any time soon -- that market will belong to Google Android and RIM for the forseeable future.

While one could increase the resolution of the display to make up some of the difference, it is meaningless unless your tablet also includes sandpaper, so that the user can sand down their fingers to around one-quarter of their present size.

Apple has done extensive user testing on user interfaces over many years, and we really understand this stuff. There are clear limits of how close you can physically place elements on a touchscreen before users cannot reliably tap, flick or pinch them. This is one of the key reasons we think the 10-inch screen size is the minimum size required to create great tablet apps.